P AST , P RESENT , AND F - UTURE OF

In the Central Great Plains, there are inces of Alberta, Manitoba, and Saskatchewan in Canada, two primary water sources for irrigation: rivers and reser- where they are called the Prairies, southward through the voirs fed by snowmelt from the Rocky Mountains and deliv- Plains states and west Texas to the northern part of the state ered as surface water through canal systems, and the High of Coahu. [...] It was not until Perhaps more relevant for farming, reference evapotranspi- the 1930s that a significant investment was made to bring ration (ETo) increases from the northeast to southwest in the surface water to areas along the North Platte River in the Central and Southern Great Plains, being considerably less Panhandle and west-central portions of Nebraska, e.g., the in the middle of Nebraska (. [...] Expansion of irrigation in the Great to lawsuits and negotiations between the states that continue Plains was greatly motivated by the drought of the 1950s and to the present in some cases and that have consequences for aided by the soldiers returning from World War II, reaching irrigation water availability. [...] As of 2018, pressurized systems supplied water to 65% The CWP is the only one of the three metrics that corre- of the irrigated area in the U. [...] For example, in 1942, the Republican River greatest (25 to 211 mm year-1) in Nebraska and northeast Compact was negotiated by the states of Colorado, Kansas, Colorado and least (<2 to 25 mm year-1) in southwest Kan- and Nebraska and a representative of the president of the sas, southeast Colorado, and the Oklahoma and Texas Pan- U.